The present invention is generally in the field of the diagnosis and treatment of ailments such as cancer, and relates to a method and system for guiding a diagnostic or therapeutic instrument towards a target region inside the patient""s body.
Diagnostic and therapeutic techniques aimed at diagnosing and treating cancerous tumors are known and widely used. Some of them involve the insertion of an instrument such as a needle, from outside the patient into a tumor that is suspected of being cancerous. For example, a biopsy needle commonly is inserted into a tumor to withdraw a tissue sample for biopsy. In brachytherapy, a radioisotope is placed at the tip of a needle, and the tip of the needle is inserted into the tumor to deliver radiation to the tumor with minimal irradiation of the surrounding healthy tissue. Although not common in medical practice, chemotherapeutic agents also may be injected into the tumor using a needle. Such needles are often inserted into the patient utilizing a series of structural images of the patient, such as ultrasound images, images obtained with Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) techniques. These images are acquired before and during the insertion of the instrument, to verify that the instrument is being directed towards the correct target and is bypassing organs such as blood vessels, which should not be penetrated by the instrument.
Since a tumor may include both cancerous tissue and non-cancerous tissue, it is important to be able to direct an instrument specifically to a cancerous portion of a tumor, and to avoid misdiagnosis from the non-cancerous portion of a tumor. In the case of a biopsy, the needle should be directed towards the portion of the tumor that is most likely to be cancerous. In the case of brachytherapy, the needle should be directed towards the cancerous portion of the tumor. Structural imaging modalities, such as CT and MRI, that have enough spatial accuracy and resolution to distinguish and resolve tumors, are nevertheless unable to differentiate cancerous tissue from non-cancerous tissue. Functional imaging modalities, including tomographic nuclear imaging modalities, such as Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), can distinguish cancerous tissue from non-cancerous tissue, but lack the spatial accuracy and resolution that is needed for the accurate positioning of instruments such as biopsy needles and brachytherapy needles.
Techniques for registering a functional image with a structural image to produce a combined image have been developed, and are disclosed, for example in the following publications: M. W. Vannier and D. E. Gayou, xe2x80x9cAutomated registration of multimodality imagesxe2x80x9d, Radiology, vol. 169 pp. 860-861 (1988); J. A. Correia, xe2x80x9cRegistration of nuclear medicine images, J. Nucl. Med., vol. 31 pp. 1227-1229 (1990); J-C Liehn, A. Loboguerrero, C. Perault and L. Demange, xe2x80x9csuperposition of computed tomography and single photon emission tomography immunoscinigraphic images in the pelvis: validation in patients with colorectal or ovarian carcinoma recurrencexe2x80x9d, Eur. J. Nucl. Med., vol. 19 pp. 186-194 (1992); F. Thomas et al., xe2x80x9cDescription of a prototype emission transmission computed tomography imaging systemxe2x80x9d, J. Nucl. Med., vol. 33 pp. 1881-1887 (1992); D. A. Weber and M. Ivanovic, xe2x80x9cCorrelative image registrationxe2x80x9d, Sem. Nucl. Med., vol. 24 pp. 311-323 (1994); and Hasegawa et al. U.S. Pat. No. 5,376,795. All six of these prior art documents are incorporated herein by reference for all purposes as if fully set forth herein. In principle, a sequence of such combined images could be used to direct an instrument to the cancerous portion of a tumor. In practice, the multiple imaging sessions and registrations that this would require make this solution impractical and possibly dangerous.
Stereotaxis is a known technique for localizing a region inside the body of a patient from outside the body of the patient, and for directing an instrument such as a needle, or a narrow beam of therapeutic radiation, to the target region. The degree of accuracy obtained from stereotaxis is relatively high, so this technique has been considered useful mainly on the brain and the breast. In stereotactic surgery of the brain, a CT localization frame is attached rigidly to the head of a patient and a CT image of the patient""s brain is acquired with the CT localization frame in place. The position of the CT localization frame in the CT image is used to position the patient with respect to a surgical instrument utilizing a source of radiation so that the beam or beams of radiation intersects the desired target. Note that the CT localization frame is removed from the patient""s head before the therapeutic irradiation commences.
Additionally, in order to access a correct location inside a patient""s body with a diagnostic or therapeutic instrument, it is desirable to have exact information on the physical dimensions of the instrument. Using existing tools, such information can be obtained by one of the following means: prompting the user to enter all relevant physical dimensions; keeping a software library of known instruments and prompting the user for a specific model type; or prompting the user to perform a series of actions with a calibration device. Needless to say, these are cumbersome and time-consuming procedures, and require caregiver assistance.
There is accordingly a need in the art to facilitate the technique of accessing a correct target region inside the patient""s body with a diagnostic or therapeutic instrument, aimed at diagnosis and therapy purposes, by providing a novel method and system for guiding the instrument towards the target region, which is not necessarily located in the head or breast.
It is a major feature of the present invention to provide such a method that utilizes a combined image of at least a portion of the patient""s body including a target region, which image is obtained by registering a high-resolution structural image and a relatively low-resolution functional image of this portion of the patient""s body.
It is a further feature of the present invention to provide such a system that utilizes a guiding device having an indicator associated with a diagnostic or therapeutic instrument for presenting data indicative of a position of the indicator relative to any other point in the chosen portion of the patient""s body.
The main idea of the present invention consists of the utilization of a combined image, obtained by registering structural and functional images of at least a portion of the patient""s body including a target region, for guiding an instrument (diagnostic or therapeutic) towards the target. The structural and functional images are obtained using, respectively, structural and functional modalities, namely suitable known techniques, and the combined image is obtained by using any known suitable technique, for example, those disclosed in the above publications.
As used herein, the term xe2x80x9ctargetxe2x80x9d refers to a structurally discrete portion in the patient""s body, such as an organ or a tumor, that is suspected of containing diseas (e.g., cancerous tissue). This diseased tissue (target) is surrounded by healthy tissues (e.g., non-cancerous tissue).
As used herein, the term xe2x80x9cinstrumentxe2x80x9d refers to a diagnostic or treatment instrument that can access and, if desired, be inserted into the target from outside the patient for the purpose of either diagnosis or treatment of a disease. Typical examples of such instruments include biopsy needles and needles for brachytherapy and chemotherapy.
According to one broad aspect of the present invention, there is provided a method for guiding an instrument towards a correct target inside the patient""s body, the method comprising the steps of:
(i) providing an image of at least a portion of the patient""s body including said target, wherein said image presents a combined image of registered structural and functional images of said at least portion of the patient""s body;
(ii) providing data indicative of a position of a location on the instrument relative to any other point in said at least portion of the patient""s body; and
(iii) directing the instrument to said target.
To provide the combined image, the structural and functional images are obtained with, respectively, structural and functional modalities and registered. While directing the instrument towards the target, at least one additional image of the at least portion of the patient""s body is preferably acquired with at least one of structural or functional modalities, for obtaining at least one additional combined image. Several additional images may be periodically or continuously acquired, and consequently, several additional combined images be obtained.
The structural and functional images used for obtaining the combined image may be, respectively, high-resolution and relatively low resolution. The resolution of 3-5 mm pixel size is considered to be low, and that of less than 1 mm pixel size is considered to be high resolution. In this case, the at least one additional image may be a low-resolution functional image or relatively higher resolution structural images (the so-called xe2x80x9cmedium-resolutionxe2x80x9d structural image). Alternatively, the structural and functional images used for obtaining the combined image may each be of low resolution, in which case the at least one additional image is acquired with high-resolution structural modality.
To provide the data indicative of the relative position of the instrument, a guiding device is used having an indicator associated with the instrument.
The guiding device may comprise a frame attachable to the patient""s body and a stereotactic guide. The indicator is in the form of at least three markers on the frame. In this case, to provide the combined image, the following steps are performed. The frame is rigidly secured to the patient, and then the high-resolution structural image is acquired using a high-resolution structural imaging modality, such as CT or MRI. This high-resolution structural image includes at least the portion of the patient""s body. The markers are used by taking a series of structural images that covers all of them, since they are located in different planes. To acquire the functional image to be registered with the so-obtained high-resolution structural image, a suitable radiopharmaceutical, that is taken up preferentially by cancerous tissue (i.e., target), is injected into the patient, and the portion of the patient""s body that was imaged with the structural modality is again imaged using a lower-resolution functional imaging modality that records radiation emitted by the radiopharmaceutical to acquire an image of the target. The structural image and the functional image are then registered to provide the combined image that shows the relative location of the target relative to other elements in the combined image. In other words, the combined image shows which part of a tumor mass seen in the structural image contains cancer, and where the cancerous areas are located on the high-resolution structural image.
Prior to performing step (iii), the stereotactic guide is rigidly attached to the frame. Since the position of the target (e.g., cancerous tissue) relative to the frame is known, the position of the target relative to the stereotactic guide is also known. The stereotactic guide then is used, under computer control, to guide the instrument, such as a biopsy needle or a brachytherapy needle, to the target, with reference to the pixels of the combined image that represent the markers and the target. The trajectory of the instrument is programmed in advance so that the instrument does not penetrate organs, such as vascular structures, that should not be penetrated.
According to another broad aspect of the invention, there is provided a method for accessing a target in a patient""s body with an instrument, the method comprising the steps of:
(a) providing a guiding device having a frame to be secured to the patient and a stereotactic guide assembly, wherein the frame carries an indicator in the form of at least three markers;
(b) rigidly securing said frame to the patient;
(c) imaging at least a portion of the patient""s body including the target, using a structural imaging modality, to produce a structural image of the at least portion of the patient""s body and at least one of the markers, and acquiring a series of images to image all the markers and estimate their location in said structural image;
(d) imaging the at least portion of the patient""s body using a functional imaging modality to produce a functional image of the at least portion of the patient""s body; and
(e) registering the functional image with the structural image to produce a combined image;
(f) rigidly attaching said stereotactic guide assembly to said frame, and
(g) directing the instrument to the target, using the stereotactic guide, with reference to said markers as imaged in the combined image.
According to another embodiment of the invention, the guiding device is a so-called tracking system composed of a guiding reference unit providing data indicative of space coordinates of the indicator that is in the form of a sensor attachable to the instrument at its handle portion, and a guiding controller. The latter is interconnected between the indicator and the guiding reference, and is connected to a computer device displaying the combined image. Such a tracking system may be of any known type, e.g., magnetic, optical, inertial, sound-waves, GPS. The construction and operation of the tracking system are known per se, and do not form part of the present invention. Therefore, the operation of the tracking system does not need to be specifically described, except to note the following. The controller is capable of tracking the position of a sensor and obtaining the information indicative of six degrees of freedom (i.e., 3 position coordinates and 3 rotation angles). The controller is installed with suitable hardware and is operated by suitable software for performing a signal processing technique and generating data indicative of the sensor""s position in the coordinate space defined by the guiding reference. The computer device analyzes this data to generate a graphic representation of instrument location on the structural or functional image, or direction instructions for guiding the instrument towards the target.
Magnetic tracking systems are based on a magnetic/electronic field transmitter (guiding reference) and a relatively small receiver (indicator). Such a system may, for example, by the miniBIRD model, commercially available from Ascension Technology Corporation. Optical tracking systems apply a visual perception technique that observes either light reflected items or small light emitters, for example POLARIS models, commercially available from Northern Digital Inc.
Additionally, the indicator may comprise an identification electronic chip attached to the handle-portion of the instrument. This is actually a chip with an embedded application, such as a miniature electronic memory chip programmed during the manufacture of the specific instrument. The chip may be equipped with a transmitting utility generating and transmitting data indicative of the physical dimensions of the instrument or its corresponding code in accordance with a coded library. Alternatively or additionally, the chip may comprise a magnetic strip or a bar code to be read by a suitable reading head associated with the computer device.
According to another broad aspect of the present invention, there is provided a system for guiding an instrument towards a correct target inside the patient""s body, the system comprising:
a computer device for displaying an image of at least a portion of the patient""s body including said target, wherein said displayed image presents a combined image of registered structural and functional images of said at least portion of the patient""s body;
a guiding device having an indicator associated with said instrument for presenting data indicative of a position of a location on the instrument relative to any other point in said at least portion of the patient""s body, said guiding device being connectable to said computer device and operable thereby for directing the instrument to said target.
Preferably, the system also comprises an additional imaging modality capable of acquiring at least one of structural and functional images of said at least portion of the patient""s body. This additional imaging modality is operable for acquiring at least one image, used for obtaining at least one additional combined image (a so-called xe2x80x9cupdated combined imagexe2x80x9d). This at least one additional combined image is utilized, while directing the instrument towards the target.
Although the scope of the present invention includes the diagnosis and treatment of any diseased tissue, the present invention is described below in terms of the primary application thereof, the diagnosis and treatment of cancer.